Three-dimensional memory device and manufacturing method thereof

ABSTRACT

A memory device includes a first stacking structure, a second stacking structure, a plurality of first isolation structures, gate dielectric layers, channel layers and channel layers. The first stacking structure includes a plurality of first gate layers, and a second stacking structure includes a plurality of second gate layers, where the first stacking structure and the second stacking structure are located on a substrate and separated from each other through a trench. The first isolation structures are located in the trench, where a plurality of cell regions are respectively confined between two adjacent first isolation structures of the first isolation structures in the trench, where the first isolation structures each includes a first main layer and a first liner surrounding the first main layer, where the first liner separates the first main layer from the first stacking structure and the second stacking structure. The gate dielectric layers are respectively located in one of the cell regions, and cover opposing sidewalls of the first stacking structure and the second stacking structure as well as opposing sidewalls of the first isolation structures. The channel layers respectively cover an inner surface of one of the gate dielectric layers. The conductive pillars stand on the substrate within the cell regions, and are laterally surrounded by the channel layers, where at least two of the conductive pillars are located in each of the cell regions, and the at least two conductive pillars in each of the cell regions are laterally separated from one another.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of and claims the prioritybenefits of U.S. application Ser. No. 17/155,085, filed on Jan. 22,2021. The prior application Ser. No. 17/155,085 claims the prioritybenefit of U.S. provisional application Ser. No. 63/045,198, filed onJun. 29, 2020. The entirety of the above-mentioned patent application ishereby incorporated by reference herein and made a part of thisspecification.

BACKGROUND

Semiconductor memories are used in integrated circuits for electronicapplications, including radios, televisions, cell phones, and personalcomputing devices, as examples. Semiconductor memories include two majorcategories. One is volatile memories; the other is non-volatilememories. Volatile memories include random access memory (RAM), whichcan be further divided into two sub-categories, static random-accessmemory (SRAM) and dynamic random-access memory (DRAM). Both SRAM andDRAM are volatile because they will lose the information they store whenthey are not powered.

On the other hand, non-volatile memories can keep data stored on them.One type of non-volatile semiconductor memory is ferroelectricrandom-access memory (FeRAM, or FRAM). Advantages of FeRAM include itsfast write/read speed and small size.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a block diagram of a three-dimensional memory in accordancewith some embodiments of the disclosure.

FIG. 2A and FIG. 2B are flow diagrams illustrating a manufacturingmethod for forming a three-dimensional memory device in accordance withsome embodiments of the disclosure.

FIG. 3A through FIG. 10A are schematic three-dimensional viewsillustrating structures at various stages during the manufacturingmethod of the three-dimensional memory device as shown in FIG. 2A andFIG. 2B.

FIG. 3B through FIG. 10B are schematic cross-sectional views along linesA-A′ shown in FIG. 3A through FIG. 10A, respectively.

FIG. 3C through FIG. 10C are schematic enlarged plan views illustratinga portion of the three-dimensional memory device at process stepsdescribed with reference to FIG. 3A through FIG. 10A, respectively.

FIG. 11A through FIG. 11D are schematic enlarged cross-sectional viewsillustrating a portion of the three-dimensional memory device of FIG.10A.

FIG. 12 is an equivalent circuit diagram of a portion of athree-dimensional memory device in accordance with some embodiments ofthe disclosure.

FIG. 13 is a schematic cross-sectional view illustrating a semiconductorstructure in accordance with some embodiments of the disclosure.

FIG. 14A and FIG. 14B are schematic various views of a three-dimensionalmemory device in accordance with some embodiments of the disclosure.

FIG. 15A and FIG. 15B are schematic various views of a three-dimensionalmemory device in accordance with some embodiments of the disclosure.

FIG. 16A and FIG. 16B are schematic various views of a three-dimensionalmemory device in accordance with some embodiments of the disclosure.

FIG. 17 is a schematic enlarged plan views illustrating a portion of thethree-dimensional memory device in accordance with some embodiments ofthe disclosure.

FIG. 18 is a schematic enlarged plan views illustrating a portion of thethree-dimensional memory device in accordance with some embodiments ofthe disclosure.

FIG. 19 is a schematic enlarged plan views illustrating a portion of thethree-dimensional memory device in accordance with some embodiments ofthe disclosure.

FIG. 20A and FIG. 20B are schematic various views of a three-dimensionalmemory device in accordance with some embodiments of the disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components, values, operations, materials,arrangements, or the like, are described below to simplify thedisclosure. These are, of course, merely examples and are not intendedto be limiting. Other components, values, operations, materials,arrangements, or the like, are contemplated. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In addition, terms, such as “first”, “second”, “third”, “fourth” and thelike, may be used herein for ease of description to describe similar ordifferent element(s) or feature(s) as illustrated in the figures, andmay be used interchangeably depending on the order of the presence orthe contexts of the description.

Three-dimensional memory is a new evolution that improves storagecapacity of the non-volatile memory. By stacking memory cellsvertically, it is possible to dramatically increase the storage capacitywithout significantly increasing footprint area of the non-volatilememory.

FIG. 1 is a block diagram of a three-dimensional memory in accordancewith some embodiments of the disclosure. Referring to FIG. 1 , in someembodiments, the three-dimensional memory includes a three-dimensionalmemory device 10, a row decoder 12, and a column decoder 14. Thethree-dimensional memory device 10, the row decoder 12, and the columndecoder 14 may each be part of a same semiconductor die, or may be partsof different semiconductor dies. For example, the three-dimensionalmemory device 10 can be part of a first semiconductor die, while the rowdecoder 12 and the column decoder 14 can be parts of a secondsemiconductor die.

In some embodiments, the three-dimensional memory device 10 includesmemory cells MC, row lines RL (such as word lines), and column lines CL(such as bit lines and/or source line). The memory cells MC are arrangedin rows and columns (e.g., in a form of array, which may be referred toas a memory array). The row lines R and the column lines CL areelectrically connected to the memory cells MC. The row lines RL areconductive lines that extend along the rows of the memory cells MC. Thecolumn lines CL are conductive lines that extend along the columns ofthe memory cells MC.

The row decoder 12 may be, e.g., a static complementarymetal-oxide-semiconductor (CMOS) decoder, a pseudo N-typemetal-oxide-semiconductor (pseudo-NMOS) decoder, or the like. Duringoperation, the row decoder 12 selects desired memory cells MC in a rowof the three-dimensional memory device 10 by activating a correspondingrow lines RL for the row. The column decoder 14 may be, e.g., a staticCMOS decoder, a pseudo-NMOS decoder, or the like, and may include writerdrivers, sense amplifiers, combinations thereof, or the like. Duringoperation, the column decoder 14 selects corresponding column lines CLfor the desired memory cells MC from columns of the three-dimensionalmemory device 10 in the selected row, and reads data from or writes datato the selected memory cells MC with the corresponding column lines CL.

FIG. 2A and FIG. 2B are flow diagram illustrating a manufacturing methodfor forming a three-dimensional memory device 10 in accordance with someembodiments of the disclosure. FIG. 3A through FIG. 10A are schematicthree-dimensional views illustrating structures at various stages duringthe manufacturing method of the three-dimensional memory device 10 asshown in FIG. 2A and FIG. 2B. FIG. 3B through FIG. 10B are schematiccross-sectional views along lines A-A′ shown in FIG. 3A through FIG.10A, respectively. FIG. 3C through FIG. 10C are schematic enlarged planviews illustrating a portion of the three-dimensional memory device 10indicated by dotted boxes B at process steps described with reference toFIG. 3A through FIG. 10A, respectively. FIG. 11A through FIG. 11D areschematic enlarged cross-sectional views illustrating a portion of thethree-dimensional memory device 10 of FIG. 10A, which are respectivelytaken along lines C-C′, D-D′, E-E′ and F-F′ shown in FIG. 10A. A portionof the three-dimensional memory device 10 is illustrated, for example.

Referring to FIG. 3A through FIG. 3C, in some embodiments, an underlyingstructure 102 is provided, and a multilayer stack 104 is formed over theunderlying structure 102, in accordance with step S100 of FIG. 2A. Theunderlying structure 102, for example, is an etching stop layer over asemiconductor substrate (not shown) to prevent any undesired damages oretches to layers underneath the underlying structure inside the CMOSintegrated circuit. The underlying structure 102 may be referred to as asubstrate of the three-dimensional memory device 10. The underlyingstructure 102 may be a semiconductor substrate, such as a bulksemiconductor substrate, a semiconductor-on-insulator (SOI) substrate,or the like, which may be doped (e.g., with a p-type or an n-typedopant) or undoped. The underlying structure 102 may be a wafer, such asa silicon wafer. Generally, an SOI substrate is a layer of asemiconductor material formed on an insulator layer. The insulator layermay be a buried oxide (BOX) layer, a silicon oxide layer, or the like.For example, the insulator layer is provided on a substrate, typically asilicon or glass substrate. Other substrates, such as a multilayered orgradient substrate may also be used. In some embodiments, thesemiconductor material of the underlying structure 102 includes silicon;germanium; a compound semiconductor including silicon carbide, galliumarsenide, gallium phosphide, indium phosphide, indium arsenide, and/orindium antimonide; an alloy semiconductor including silicon germanium,gallium arsenide phosphide, aluminum indium arsenide, aluminum galliumarsenide, gallium indium arsenide, gallium indium phosphide, and/orgallium indium arsenide phosphide; or combinations thereof. Theunderlying structure 102 may include a dielectric material. For example,the underlying structure 102 is a dielectric substrate, or include adielectric layer on a semiconductor substrate. Acceptable dielectricmaterials for dielectric substrates may include oxides such as siliconoxide; nitrides such as silicon nitride; carbides such as siliconcarbide; the like; or combinations thereof such as silicon oxynitride,silicon oxycarbide, silicon carbonitride, or the like. In someembodiments, as shown in FIG. 3A, the underlying structure 102 is formedof silicon carbide.

In some embodiments, the multilayer stack 104 includes alternating firstdielectric layers 104A and second dielectric layers 104B. For example,the first dielectric layers 104A are formed of a first dielectricmaterial, and the second dielectric layers 104B are formed of a seconddielectric material. The first dielectric material and the seconddielectric material may each be selected from the candidate dielectricmaterials of the underlying structure 102. The first dielectric materialis different from the second dielectric material, in some embodiments.As illustrated in FIG. 3A through FIG. 10C, the multilayer stack 104includes five layers of the first dielectric layers 104A and four layersof the second dielectric layers 104B for illustrative purposes; however,the disclosure is not limited thereto. It should be appreciated that themultilayer stack 104 may include any number of the first dielectriclayers 104A and the second dielectric layers 104B.

The multilayer stack 104 will be patterned in subsequent processingdepicted in FIGS. 4A-4C through FIGS. 10A-10C to form trenches andtransistors formed in the trenches. As such, the dielectric materials ofthe first dielectric layers 104A and the second dielectric layers 104Bboth have a high etching selectivity from the etching of the underlyingstructure 102. In other words, for example, the underlying structure 102is an etching stop layer formed over a CMOS integrated circuit. Thepatterned first dielectric layers 104A are insulating layers, which willbe used to isolate the subsequently formed transistors. The patternedsecond dielectric layers 104B are sacrificial layers (or dummy layers),which will be removed in subsequent processing and replaced with wordlines for the transistors. As such, the second dielectric material ofthe second dielectric layers 104B also has a high etching selectivityfrom the etching of the first dielectric material of the firstdielectric layers 104A. In other words, the first dielectric layers 104Acould remain substantially intact during removal of the seconddielectric layers 104B . In embodiments where the underlying structure102 is formed of silicon carbide, the first dielectric layers 104A canbe formed of an oxide such as silicon oxide, and the second dielectriclayers 104B can be formed of a nitride such as silicon nitride. Othercombinations of dielectric materials having acceptable etchingselectivity from one another may also be used.

Each layer of the multilayer stack 104 may be formed by an acceptabledeposition process such as chemical vapor deposition (CVD) such asplasma-enhanced chemical vapor deposition (PECVD) or flowable chemicalvapor deposition (FCVD), atomic layer deposition (ALD), or the like. Athickness of each of the layers may be in the range of about 15 nm toabout 90 nm. In some embodiments, the first dielectric layers 104A areformed to a different thickness than the second dielectric layers 104B.For example, the first dielectric layers 104A can be formed to a firstthickness T1 and the second dielectric layers 104B can be formed to asecond thickness T2, with the second thickness T2 being from about 0% toabout 100% greater than or less than the first thickness T1. Themultilayer stack 104 can have an overall height H in the range of about1000 nm to about 50000 nm. In the disclosure, FIG. 3C through FIG. 10Ceach schematically illustrate the enlarged plan view of a portion thethree-dimensional memory device 10 depicted in the boxes B that is at alevel where one second dielectric layer 104B located in, for example.

Referring to FIG. 4A through FIG. 4C, in some embodiments, trenches 106are formed in the multilayer stack 104, in accordance with step S102 ofFIG. 2A. For example, as shown in FIG. 4A and FIG. 4B, the trenches 106extend through the multilayer stack 104 and expose the underlyingstructure 102. In alternative embodiments, the trenches 106 extendthrough some but not all layers of the multilayer stack 104. Thetrenches 106 may be formed using acceptable photolithography and etchingtechniques, such as with an etching process that is selective to themultilayer stack 104 (e.g., etches the dielectric materials of the firstdielectric layers 104A and the second dielectric layers 104B at a fasterrate than the material of the underlying structure 102). The etching maybe any acceptable etch process, such as a reactive ion etch (RIE), aneutral beam etch (NBE), the like, or a combination thereof. The etchingmay be anisotropic. In embodiments where the underlying structure 102 isformed of silicon carbide, the first dielectric layers 104A are formedof silicon oxide, and the second dielectric layers 104B are formed ofsilicon nitride, the trenches 106 can be formed by a dry etch using afluorine-based gas (e.g., C₄F₆) mixed with hydrogen (H₂) or oxygen (O₂)gas. As shown in FIG. 4A through FIG. 4C, a portion of the multilayerstack 104 is disposed between each pair of the trenches 106, forexample. In some embodiments, sidewalls SW104A of the first dielectriclayers 104A and sidewalls SW104B of the second dielectric layers 104Bare exposed by the trenches 106. The sidewalls SW104A of the firstdielectric layers 104A may be substantially coplanar to and levelledwith the sidewalls SW104B of the second dielectric layers 104B.

Referring to FIG. 5A through FIG. 5C, in some embodiments, the seconddielectric layers 104B are selectively removed, in accordance with stepS104 of FIG. 2A. By removing the second dielectric layers 104B, recesses108 are formed to expose surfaces of the first dielectric layers 104Apreviously in contact with the second dielectric layers 104B, forexample. In some embodiments, the trenches 106 and the recesses 108 arespatially communicated to each other.

The recesses 108 may be formed by an acceptable etching process, such asone that is selective to the material of the second dielectric layers104B (e.g., selectively etches the material of the second dielectriclayers 104B at a faster rate than the materials of the first dielectriclayers 104A and the underlying structure 102). The etching may beisotropic. In embodiments where the underlying structure 102 is formedof silicon carbide, the first dielectric layers 104A are formed ofsilicon oxide, and the second dielectric layers 104B are formed ofsilicon nitride, the trenches 106 can be expanded by a wet etch usingphosphoric acid (H₃PO₄). In alternative embodiments, a dry etchselective to the material of the second dielectric layers 104B may beused. Due to the first dielectric layers 104A could remain substantiallyintact during removal of the second dielectric layers 104B, the recesses108 each can have a thickness substantially equal to the thickness T2 ofthe second dielectric layers 104B. Further, a periphery regionsurrounding an array region with a memory array (included in thethree-dimensional memory device 10) has some portions of the seconddielectric layers 104B that are not removed (e.g., during thereplacement process described in FIG. 5A through FIG. 5C and FIG. 6Athrough FIG. 6C). Therefore, some portions of the second dielectriclayers 104B in the periphery region also provides further support toprevent the first dielectric layers 104A in the array region fromcollapse.

Referring to FIG. 6A through FIG. 6C, in some embodiments, conductivelayers 110 are formed in the recesses 108, in accordance with step S106of FIG. 2A. In some embodiments, the previously existed seconddielectric layers 104B are replaced by the conductive layers 110. Forexample, the first dielectric layers 104A and the conductive layers 110are stacked on the underlying structure 102 in alternation, and togetherform a plurality of stacking structures 112. The stacking structures 112are laterally spaced apart from one another by the trenches 106, anddirectly stand on the underlying structure 102. In some embodiments,sidewalls SW110 of the conductive layers 110 are substantially coplanarto and levelled with the sidewalls SW104A of the first dielectric layers104A, as shown in FIG. 6B. The sidewalls SW110 of the conductive layers110 and the sidewalls SW104A of the first dielectric layers 104A maytogether referred to as sidewalls SW112 of the stacking structures 112.For example, the sidewalls SW112 of the stacking structures 112 aresubstantially vertical sidewalls being substantially planar and flat, asshown in FIG. 6A and FIG. 6B. In other words, the sidewalls SW112 of thestacking structures 112 are continuously vertical sidewalls. Forexample, in a cross-section of FIG. 6B, the sidewalls SW112 include asubstantially straight line. The conductive layers 110 may be formed ofa conductive material, such as a metal, such as tungsten, ruthenium,molybdenum, cobalt, aluminum, nickel, copper, silver, gold, alloysthereof, or the like. The conductive layers 110 may each be formed by anacceptable deposition process such as CVD, ALD, or the like.

A method for forming the conductive layers 110 may include, but notlimited to, filling up the trenches 106 and the recesses 108 between thefirst dielectric layers 104A (shown in FIG. 5A) with the conductivematerial by a deposition process, such as a CVD process or an ALDprocess. Thereafter, portions of the conductive material not covered bythe first dielectric layers 104A are removed by an etching process (e.g.a “etch-back” process). The remained portions of the conductive materialform the conductive layers 110. In other words, the first dielectriclayers 104A may be functioned as shadow masks during such etchingprocess, and such patterning of the conductive material can beconsidered as a self-aligning process. An acceptable etch process, suchas a dry etch (e.g., RIE, NBE, the like), a wet etch, the like, or acombination thereof, may be performed to remove excess conductivematerial from the sidewalls of the first dielectric layers 104A and thetop surface of the underlying structure 102. The etching may beanisotropic or isotropic. Each of the conductive layers 110 can have asimilar overall thickness T2 as the second dielectric layers 104B(discussed above with respect to FIG. 3A). Up to here, the replacementof second dielectric layers 104B with the conductive material iscompleted. In the disclosure, the conductive layers 110 may be referredto as gate layers. The conductive layers 110 may act as the gates of thetransistors.

Furthermore, although not shown, end portions of some of the stackingstructures 112 may be shaped into staircase structures, of which an endportion of each film (one first dielectric layer 104A or one seconddielectric layer 104B) of the multilayer stack 104 may be protruded withrespect to an overlying film. One or more sides of the multilayer stack104 is/are shaped into staircase structure(s) before forming thetrenches 106. In these embodiments, the staircase structure(s) is/areformed by a staircase-first process. The first dielectric layers 104Aand/or the second dielectric layers 104B may respectively be exposed atsteps of the staircase structure(s). A method for shaping the multilayerstack 104 to form the staircase structure(s) may include a trim-and-etchprocess. Furthermore, a dielectric layer (not shown) may be subsequentlyformed on the multilayer stack 104 having the staircase structure. A topsurface of this dielectric layer may be leveled with a top surface ofthe multilayer stack 104. With such, as the second dielectric layers104B are removed and replaced with the conductive layers 110, theconductive layers 110 and the respective first dielectric layer 104Aincluded in each of the stacking structures 112 is in a form of thestaircase structure.

Additionally, one or more glue layers 111 (or referred to as barrierlayers) may be formed between the first electric layers 104A and theconductive layers 110. In some embodiments, as shown in FIG. 6B, theglue layers 111 each extend along the sides (e.g., top surface and thebottom surface in contact with the first dielectric layers 104A) of aconductive layer 110. The glue layers 111 are formed of a conductivematerial different from the material of the conductive layers 110, suchas a metal nitride. For example, the material of the glue layers 111includes titanium nitride, tantalum nitride, molybdenum nitride,zirconium nitride, hafnium nitride, or the like. The material of theglue layers 111 is one has good adhesion to the material of the firstdielectric layers 104A, and the material of the conductive layers 110 isone that has good adhesion to the material of the glue layers 111. Forone example, the first dielectric layers 104A are formed of an oxidesuch as silicon oxide, the glue layers 111 can be formed of titaniumnitride and the conductive layers 110 can be formed of tungsten.Besides, each glue layer 111 can have a thickness less than thethickness T1 of the first dielectric layers 104A and the thickness ofthe conductive layers 110, where a sum of the overall thickness of theglue layers 111 and the thickness of a corresponding conductive layers110 located in one recess 108 is equal to the thickness (e.g. T2) ofsuch recess 108. Due to the glue layers 111, the adhesion between thefirst dielectric layers 104A and the conductive layers 110 in each ofthe stacking structures 112 is enhanced. The glue layers 111 will beomitted in the following drawings for simplicity and illustrativepurposes.

Referring to FIG. 7A through FIG. 7C, in some embodiments, dummydielectric structures 113 m are formed in the trenches 106, inaccordance with step S108 of FIG. 2A. For example, the dummy dielectricstructures 113 m are formed to fill up the trenches 106, where sidewallsSW112 of the stacking structures 112 are in contact with the dummydielectric structures 113 m. The dummy dielectric structures 113 m areformed of a dielectric material. Acceptable dielectric materials mayinclude oxides such as silicon oxide or aluminum oxide; nitrides such assilicon nitride; carbides such as silicon carbide; the like; orcombinations thereof such as silicon oxynitride, silicon oxycarbide,silicon carbonitride, or the like. The material of the dummy dielectricstructure 113 m may be the same as the material of the first dielectriclayers 104A or the material of the second dielectric layers 104B.Alternatively, the material of the dummy dielectric structure 113 m maybe different from the material of the first dielectric layers 104Aand/or the material of the second dielectric layers 104B. The disclosureis not limited thereto.

A method for forming the dummy dielectric structures 113 m may include,but not limited to, filling up the trenches 106 with the dielectricmaterial by a deposition process, such as CVD or the like. Subsequently,a planarization process may be performed to remove portions of thedielectric material above illustrated top surfaces of the stackingstructures 112. The planarization process may include a chemicalmechanical polish (CMP) process, an etching process (e.g. etch-back) ora combination thereof. The remained portions of the dielectric materiallocated within the trenches 106 form the dielectric structures 113 m. Asshown in FIG. 7B, illustrated top surfaces of the dummy dielectricstructures 113 m are substantially coplanar to and levelled with theillustrated top surfaces of the stacking structures 112, for example.

Referring to FIG. 7A through FIG. 7C and FIG. 8A through FIG. 8Ctogether, in some embodiments, portions of the dummy dielectricstructure 113 m are removed to form a plurality of cell regions CRseparated from one another, in accordance with step S110 of FIG. 2A. Forexample, the dummy dielectric structures 113 m of the trenches 106 arepartially removed to form the cell regions CR, where non-removed dummydielectric structure 113 m in the trenches 106 form remained dummydielectric structures 113 separating the cell regions CR from oneanother. The cell regions CR may penetrate through the remained dummydielectric structures 113 to partially expose the top surface of theunderlying structure 102 and the sidewalls SW112 of the stackingstructures 112. A method for forming the cell regions CR may include,but not limited to, patterning dummy dielectric structure 113 m by usinga photolithography process and an etching process to partially removethe dummy dielectric structure 113 m. The etching may be any acceptableetch process, such as RIE, NBE, the like, or a combination thereof. Theetching may be anisotropic.

After the formation of the cell regions CR, film stacks may be formed inthe cell regions CR. The film stacks each may include one dielectriclayer 114, one semiconductor layer 116 and one conductive material 118m, and may be formed in one of the cell regions CR.

Dielectric layers 114 are respectively formed on the sidewalls SW1 ofthe cell regions CR, in accordance with step S112 of FIG. 2A. Forexample, the dielectric layers 114 are formed on the exposed top surfaceof the underlying structure 102 as well as the exposed sidewalls SW112of the stacking structures 112, as shown in FIG. 8A and 8B. In otherwords, the dielectric layers 114 may be respectively formed in one ofthe cell regions CR. As described above, the cell regions CR can beprevented from communicating with one another due to the dummydielectric structures 113. Therefore, the dielectric layers 114respectively formed in one of the cell regions CR can be separated fromone another. Further, as shown in FIG. 8A and FIG. 8C, the dielectriclayers 114 may respectively be formed as having an annular top viewshape. For example, a top view (on a X-Y plane depicted in FIG. 8C) ofeach dielectric layer 114 may appear as a substantially rectangularannulus. In some embodiments, in a cross section as indicated in FIG. 8Balong a direction Z, the dielectric layers 114 conformally cover thesidewalls SW112 of the stacking structures 112 and the top surface ofthe underlying structure 102 being exposed by the cell regions CR.

In some embodiments, the dielectric layers 114 are data storage layers(or films) formed of an acceptable ferroelectric material for storingdigital values, such as hafnium zirconium oxide (HZO); zirconium oxide(ZrO); hafnium oxide (HfO) doped with lanthanum (La), silicon (Si),aluminum (Al), or the like; undoped hafnium oxide (HfO); or the like.Alternatively, the dielectric layers 114 may be charge trap layers (orfilms). The charge trap layers may include oxide-nitride-oxide (ONO)layers. In some embodiments, a method for forming the dielectric layers114 includes globally forming a dielectric layer to conformally coverthe structure as shown in FIG. 7A by a deposition process (e.g., CVD,ALD, physical vapor deposition (PVD), or the like) or an epitaxialprocess. Subsequently, portions of the dielectric layer above theillustrated top surfaces of the stacking structures 112 may be removedby, for example, a polishing process (e.g., a CMP process), an etchingprocess or a combination thereof. The remained portions of thedielectric layer form the dielectric layers 114. In some embodiments,the dielectric layers 114 are individually referred to as memory layers(or films). On the other hands, the dielectric layers 114 may act as thegate dielectric layers of the transistors.

Semiconductor layers 116 are formed on the dielectric layers 114, inaccordance with step S114 of FIG. 2A. The semiconductor layers 116 maybe formed on inner surfaces S1 of the dielectric layers 114,respectively. As similar to the dielectric layers 114, the semiconductorlayers 116 are respectively formed in one of the cell regions CR, andare ensured to be separated from one another. Also, the semiconductorlayers 116 may respectively have an annular top view shape. For example,the top view of each semiconductor layer 116 may appear as asubstantially rectangular annulus. In some embodiments, thesemiconductor layers 116 conformally cover the sidewalls SW112 of thestacking structures 112, as shown in FIG. 8B. Furthermore, in someembodiments, the semiconductor layers 116 span on the sidewalls SW112 ofthe stacking structures 112, but may not laterally span on the topsurfaces of the substrate 102 (as shown in FIG. 8A and FIG. 8B). Inthese embodiments, some portions of the dielectric layers 114 lying onthe top surfaces of the underlying structure 102 may not be covered bythe semiconductor layers 116. In addition, each semiconductor layer 116can be regarded as being discontinuous at its bottommost region, and thesubsequently formed conductive pillars (e.g., later-formed conductivepillars 118 to be described with reference to FIG. 9A-9C) in each cellregion CR can be prevented from being electrically connected with eachother through an underlying path, which may be barely controlled by agate voltage applied to the conductive layers 110. In the disclosure,the semiconductor layers 116 may be referred to as channellayers/regions of the transistors.

In some embodiments, the semiconductor layers 116 are formed of anacceptable semiconductor material for functioning as the channel regionsof the transistors. In some embodiments, the acceptable semiconductormaterial is a metal oxide material, such as an indium-based oxidematerial (e.g., indium gallium zinc oxide (IGZO), indium tin oxide(ITO), indium gallium zinc tin oxide (IGZTO), zinc oxide (ZnO)),polysilicon, amorphous silicon, or the like. In addition, in someembodiments, a method for forming the semiconductor layers 116 includesglobally forming a semiconductor layer to conformally cover thedielectric layers 114, the underlying structure 102 and the stackingstructures 112 by a deposition process (e.g., CVD, ALD or PVD).Subsequently, portions of the semiconductor layer above the top surfacesof the stacking structures 112 as well as portions of the semiconductorlayer lying on the underlying structure 102 may be removed by, forexample, etching. The remained portions of the semiconductor layer formthe semiconductor layers 116. The etching may be any acceptable etchprocess, such as RIE, NBE, the like, or a combination thereof. Theetching may be anisotropic.

Thereafter, conductive structures 118 m are formed to fill up the cellregions CR, in accordance with step S116 of FIG. 2A. As shown in FIG. 8Athrough FIG. 8C, for example, the conductive structures 118 mrespectively stand in one of the cell regions CR, and are laterallysurrounded by the semiconductor layers 116 and the dielectric layers114. The conductive structures 118 m may be continuously formed on innersurfaces S2 of the semiconductor layers 116, respectively. For example,the semiconductor layer 116 are respectively sandwiched between thedielectric layers and the conductive structures 118 m. In thoseembodiments where the semiconductor layers 116 do not laterally span onthe top surfaces of the underlying structure 102, the conductivestructures 118 m may stand on the bottommost portions of the dielectriclayers 114. The conductive structures 118 m are formed of a conductivematerial. Acceptable conductive materials include metals such astungsten, cobalt, aluminum, nickel, copper, silver, gold, alloysthereof, or the like.

A method for forming the conductive structures 118 m includes filling upthe cell regions CR with the conductive material by a deposition processsuch as ALD or CVD, an acceptable plating technique such aselectroplating or electroless plating, or the like. Subsequently, aplanarization process may be performed to remove portions of theconductive material above the top surfaces of the stacking structures112, and the planarization process may include a CMP process, an etchingprocess (e.g. etch-back) or a combination thereof. The remained portionsof the conductive material form the conductive structures 118 m. In someembodiments, the conductive structures 118 m are made of tungsten.Additional glue layers may be formed between the conductive structures118 m and the semiconductor layers 116; similar to the conductive layers110, the use of glue layers depends on the conductive material of theconductive structures 118 m.

Referring to FIG. 9A through FIG. 9C, in some embodiments, portions ofthe conductive structures 118 m are removed to form conductive pillars118 within the cell regions CR, in accordance with step S118 of FIG. 2A.For example, the conductive structures 118 m within the cell regions CRare partially removed to form a plurality of first recesses R1, wherenon-removed conductive structures 118 m in each of the cell regions CRform a pair of the conductive pillars 118 separating from one another byone first recess R1. The first recesses R1 may penetrate through theconductive pillars 118 to partially expose top surfaces of thebottommost portions of the dielectric layers 114, sidewalls SW116 of thesemiconductor layers 116 and sidewalls SW118 of the conductive pillars118.

A method for forming the first recesses R1 may include, but not limitedto, patterning the conductive structures 118 m by using aphotolithography process and an etching process to partially remove theconductive structure 118 m to form multiple pairs of the conductivepillars 118. The etching may be any acceptable etch process, such asRIE, NBE, the like, or a combination thereof. The etching may beanisotropic. In the disclosure, the conductive pillars 118 may bereferred to as source/drain regions of the transistors. The conductivepillars 118 may be conductive columns formed in pairs, with eachsemiconductor layer 116 contacting a corresponding pair of theconductive pillars 118 in each cell region CR. Up to here, thetransistors formed in the trenches 106 of the three-dimensional memorydevice 10 are manufactured. Each transistor at least includes a pair ofconductive pillars 118 (acting as the source/drain regions), aconductive layer 110 (acting as the gate), and the regions of thesemiconductor layer 116 (acting as the channel region) and thedielectric layer 114 (acting as the gate dielectrics) intersecting theconductive layer 110 and between the pair of the conductive pillars 118.

In some embodiments, the remained dummy dielectric structures 113 areremoved to form a plurality of second recesses separating the cellregions CR, in accordance with step S120 of FIG. 2A. For example, theremained dummy dielectric structures 113 each located between twoadjacent cell regions CR are completely removed to form the secondrecesses R2, where the cell regions CR located in one trench 106 arephysically separated from one another by a corresponding second recessR2. The second recesses R2 may extending through the trenches 106 in thedirection Z to partially expose the top surface of the underlyingstructure 102 as well as sidewalls SW118 of the conductive pillars 118and the sidewalls SW1 (e.g., outer surfaces of the dielectric layer 114not in contact with the stacking structures 112) of the cell regions CR.A method for forming the second recesses R2 may include, but not limitedto, removing the remained dummy dielectric structures 113 by using aphotolithography process and an etching process to completely remove theremained dummy dielectric structures 113. The etching may be anyacceptable etch process, such as RIE, NBE, the like, or a combinationthereof. The etching may be anisotropic.

In one embodiment, the formation of the conductive pillars 118 isperformed prior to the removal of the remained dummy dielectricstructures 113, as described in the illustrated embodiments. However,the disclosure is not limited thereto; alternatively, the formation ofthe conductive pillars 118 is performed after the removal of theremained dummy dielectric structures 113.

Referring to FIG. 10A through FIG. 10C, in some embodiments, isolationstructures (e.g., 128, 130) are formed in the trenches 106, inaccordance with step S122 of FIG. 2A. The isolation structures mayinclude a plurality of first isolation structures 128 formed in thefirst recesses R1 within the cell regions CR and a plurality of secondisolation structures 130 formed in the second recesses R2 between twoadjacent cell regions CR, in each trench 106. The first isolationstructures 128 each electrically isolate and physically separate thepair of the conductive pillars 118 from each other in each cell regionCR. On the other hand, the second isolation structures 130 eachelectrically isolate and physically separate the laterally adjacent cellregions CR from each other. Owing to the first isolation structures 128and the second isolation structures 130, the cross-talking among theneighboring transistors located vertically and horizontally are greatlysuppressed, thereby the reliability of electrical performance of thetransistors is ensured. In some embodiments, the first isolationstructures 128 each include a first liner 120 and a first main layer124. Similar to the first isolation structures 128, for example, thesecond isolation structures 130 each include a second liner 122 and asecond main layer 126. The details of the first isolation structures 128and the second isolation structures 130 will be discussed in greaterdetail in conjunction with FIG. 11A and FIG. 11D in addition to FIG. 2B,FIG. 10A and FIB. 10C.

The first liners 120 may be respectively formed on sidewalls S5 of thefirst recesses R1, in accordance with step S122 a of FIG. 2B. Forexample, as shown in FIG. 11A and FIG. 11B, the first liners 120 areconformally formed in the first recesses R1 to cover (e.g., in contactwith) the sidewalls SW118 of the conductive pillars 118 and thesidewalls SW116 of the semiconductor layers 116 and further extend overthe top surfaces of the bottommost portions of the dielectric layers114. In other words, the first liners 120 completely cover (e.g., incontact with) the bottommost portions of the dielectric layers 114exposed by the semiconductor layers 116 and the conductive pillars 118.Further, as shown in FIG. 10A and FIG. 10C, the first liners 120 mayrespectively be formed as having an annular top view shape. A top view(on the X-Y plane depicted in FIG. 10C) of each first liner 120 mayappear as a substantially rectangular annulus. In some embodiments, athickness T3 of the first liners 120 is approximately ranging from 2 nmto 5 nm. The thickness T3 of the first liners 120 may be about 10 nm orless.

On the other hand, first liners 120 may be respectively formed onsidewalls S6 of the second recesses R2, in accordance with step S122 bof FIG. 2B. For example, as shown in FIG. 11C and FIG. 11D, the secondliners 122 is conformally formed in the second recesses R2 to cover(e.g., in contact with) the sidewalls SW1 of the cell regions CR and thesidewalls SW112 of the stacking structures 112 and further extend overthe top surfaces of the underlying structure 102. In other words, thesecond liners 122 completely cover (e.g., in contact with) the topsurfaces of the underlying structure 102 exposed by the cell regions CRand the stacking structures 112. Further, as shown in FIG. 10A and FIG.10C, the second liners 122 may respectively be formed as having anannular top view shape. A top view (on the X-Y plane depicted in FIG.10C) of each second liner 122 may appear as a substantially rectangularannulus. In some embodiments, in a cross section as indicated in FIG.10B along the direction Z, the second liners 122 conformally cover thesidewalls SW112 of the stacking structures 112 and the top surface ofthe underlying structure 102 being exposed by the cell regions CR. Insome embodiments, a thickness T4 of the second liners 122 isapproximately ranging from 2 nm to 5 nm. The thickness T4 of the secondliners 122 may be about 10 nm or less.

In some embodiments, the first liners 120 and the second liners 122 eachare formed of an acceptable dielectric material. The acceptabledielectric material may include oxides such as silicon oxide; nitridessuch as silicon nitride; carbides such as silicon carbide; the like; orcombinations thereof such as silicon oxynitride, silicon oxycarbide,silicon carbonitride, or the like. In some embodiments, a method forforming the first and second liners 120, 122 includes globally forming adielectric layer to conformally cover the structure as shown in FIG. 9Aby ALD. Subsequently, portions of the dielectric layer above theillustrated top surfaces of the stacking structures 112 may be removedby, for example, a polishing process (e.g., a CMP process), an etchingprocess or a combination thereof. The remained portions of thedielectric layer form the first and second liners 120, 122. That is, insome embodiments, the first and second liners 120, 122 aresimultaneously formed in the same step. However, the disclosure is notlimited thereto; alternatively, the first liners 120 may be formed priorto forming the second liners 122. Or, the first liners 120 may be formedafter forming the second liners 122. In other words, the material of thefirst liners 120 may be the same as the material of the second liners120. Alternatively, the material of the first liners 120 may bedifferent from the material of the second liners 120.

The first main layers 124 may be formed to fill up the first recessesR1, thereby forming the first isolation structures 128 in the firstrecesses R1, in accordance with step S122 c of FIG. 2B. The sidewalls S5of the first recesses R1 may also referred to as sidewalls of the firstisolation structures 128. For example, the first main layers 124 arecontinuously formed on inner surfaces S3 of the first liners 120 in thefirst recesses R1 to cover (e.g., in contact with) the inner surfaces S3of the first liners 120 and further extend over bottommost portions ofthe first liners 120 stacked on the bottommost portions of thedielectric layer 114. In other words, the first main layers 124completely cover (e.g., in contact with) the bottommost portions of thefirst liners 120 inside the cell regions CR. Further, as shown in thetop view of FIG. 10C, the first main layers 124 may be in contact withand enclosed by the first liners 120, respectively. In some embodiments,the first liners 120 are sandwiched between the first main layer 124 andthe conductive pillars 118 (e.g. along the direction Y) and between thefirst main layer 124 and the semiconductor layers 116 (e.g. along thedirection X), as shown in FIG. 11A and FIG. 11B. For example, in thecross-sections of FIG. 11A and FIG. 11B, the first liners 120 eachconformally cover sidewalls and a bottom surface of the first mainlayers 124, respectively. The first liners 120 may have a bowl-shape ora U-shape in the cross section to surround the first main layers 124. Insome embodiments, the first isolation structures 128 each are referredto as dielectric plugs disposed between the conductive pillars 118 inthe cell regions CR. In other words, each first isolation structure 128is disposed between the source/drain regions (e.g., a corresponding pairof conductive pillars 118) of one transistor. That is, for one cellregion/transistor, the conductive pillars 118 being paired are disposedat opposing sides of a corresponding first isolation structure 128.Thus, each first isolation structure 128 physically and electricallyseparates adjacent conductive pillars 118 in one transistor.

In some embodiments, the first main layers 124 are formed of anacceptable first dielectric material. The acceptable first dielectricmaterial may include oxides such as silicon oxide; nitrides such assilicon nitride; carbides such as silicon carbide; the like; orcombinations thereof such as silicon oxynitride, silicon oxycarbide,silicon carbonitride, or the like. Alternatively, the acceptable firstdielectric material may include a low-K (LK) dielectric material with adielectric constant lower than 3.9 or an extreme low-k (ELK) dielectricmaterial with a dielectric constant lower than 2.6. The first dielectricmaterial may be formed to fill up the first recesses R1 so as to formthe first main layer 124 by CVD (such as PECVD, FCVD), spin coating orthe like, thereby forming the first isolation structures 128 in the cellregions CR. Due to the first liners 120 are formed by ALD, a structureof the first liners 120 is finer (e.g., less void and/or smaller voidsize) than a structure of the first main layer 124, and an interface maypresent at a location where the first liners 120 and the first mainlayer 124 being joined together. In some embodiments, an etching rate ofthe first liners 120 to the first main layers 124 is approximately 1:5.Owing to the first liners 120, a metal filling leakage path formationbetween the conductors (e.g. the conductive pillars 118) in each cellregions CR or in each transistor can be prevented or greatly suppressed,and thereby improving the performance of the three-dimensional memorydevice 10.

Similar to the first main layers 124, the second main layers 126 may beformed to fill up the second recesses R2, thereby forming the secondisolation structures 130 in the first recesses R2, in accordance withstep S122 d of FIG. 2B. The sidewalls S6 of the second recesses R2 mayalso referred to as sidewalls of the second isolation structures 130.For example, the second main layers 126 are continuously formed on innersurfaces S4 of the second liners 122 in the second recesses R2 to cover(e.g., in contact with) the inner surfaces S4 of the second liners 122and further extend over bottommost portions of the second liners 122stacked on the top surface of the underlying structure 102. In otherwords, the second main layers 126 completely cover (e.g., in contactwith) the bottommost portions of the second liners 122 inside the cellregions CR as shown in FIG. 10B. Further, as shown in the top view ofFIG. 10C, the second main layers 126 may be in contact with and enclosedby the second liners 122, respectively. For example, the second liners122 are sandwiched between the second main layer 126 and the cellregions CR (e.g. along the direction Y) and between the second mainlayer 126 and the conductive layers 110 (e.g. along the direction X), asshown in FIG. 11C and FIG. 11D. For example, in the cross-sections ofFIG. 11C and FIG. 11D, the second liners 122 each conformally coversidewalls and a bottom surface of the second main layers 126,respectively. The second liners 122 may have a bowl-shape or a U-shapein the cross section to surround the second main layers 126. In someembodiments, the second isolation structures 130 each are referred to asdielectric plugs disposed between a conductive pillar 118 of one cellregion CR and a conductive pillar 118 of another cell region CR. Inother words, each second isolation structure 130 is disposed between oneof the source/drain regions of one transistor and one of thesource/drain regions of another transistor. In other words, theconductive pillars 118 being paired in one cell region CR/ transistorand the conductive pillars 118 being paired in another cell regionCR/transistor are disposed at opposing sides of a corresponding secondisolation structure 130. Thus, each second isolation structure 130physically and electrically separates adjacent cell regionsCR/transistor.

In some embodiments, the second main layers 126 are formed of anacceptable second dielectric material. The acceptable second dielectricmaterial may include oxides such as silicon oxide; nitrides such assilicon nitride; carbides such as silicon carbide; the like; orcombinations thereof such as silicon oxynitride, silicon oxycarbide,silicon carbonitride, or the like. Alternatively, the acceptable seconddielectric material may include a low-K (LK) dielectric material with adielectric constant lower than 3.9 or an extreme low-k (ELK) dielectricmaterial with a dielectric constant lower than 2.6. The seconddielectric material may be formed to fill up the second recesses R2 soas to form the second main layer 126 by CVD (such as PECVD, FCVD), spincoating or the like, thereby forming the second isolation structures 130outside the cell regions CR. The second dielectric material may be thesame as the first dielectric material. Alternatively, the seconddielectric material may be the different from the first dielectricmaterial. Due to the second liners 122 are formed by ALD, a structure ofthe second liners 122 is finer (e.g., less void and/or smaller voidsize) than a structure of the second main layer 126, and an interfacemay present at a location where the second liners 122 and the secondmain layer 126 being joined together. In some embodiments, an etchingrate of the second liners 122 to the second main layers 126 isapproximately 1:5. Owing to the second liners 122, a metal fillingleakage path formation between the conductors (e.g. the conductive layer110) among the neighboring cell regions CR or among the neighboringtransistors can be prevented or greatly suppressed, and therebyimproving the performance of the three-dimensional memory device 10.

The first and second main layers 124 and 126 may be simultaneouslyformed in the same step. In some embodiments, a method for forming thefirst and second main layers 124 and 126 includes forming a dielectriclayer in a blanket manner to cover up the structure as shown in FIG. 9Aby CVD such as PECVD or FCVD. Subsequently, portions of the dielectriclayer above the illustrated top surfaces of the stacking structures 112may be removed by, for example, a polishing process (e.g., a CMPprocess), an etching process or a combination thereof. The remainedportions of the dielectric layer form the first and second main layers126 and 128. In such embodiments, the materials of the first and secondmain layers 124 and 126 are the same. However, the disclosure is notlimited thereto; alternatively, the first main layers 124 may be formedprior to forming the second main layers 126. Or, the first main layers124 may be formed after forming the second main layers 126. In otherwords, the material of the first and second main layers 124 and 126 maybe the same or different. Up to here, the three-dimensional memorydevice 10 is manufactured.

In some embodiments, a total volume of the first and second liners 120,122 is A1, a total volume of one trench 106 (e.g. between two adjacentstacking structures 112) is B1, and a ratio of A1 to B1 is 10% or more.In some embodiments, a volume of the first liners 120 is A2, a totalvolume of one cell region CR is B2, and a ratio of A2 to B2 isapproximately ranging from 10% to 25%. In the disclosure, the first andsecond liners 120, 122 of the first and second isolation structures 128,130 act as the shielding layers for preventing metal filling leakagepaths formation inside a single one cell region CR or among neighboringcell regions CR between the conductors (e.g. the adjacent conductivepillars 118 depicted in FIG. 11A and the adjacent conductive layers 110depicted in FIG. 11D) to improve the device performance of thethree-dimensional memory device 10.

As shown in the three-dimensional memory device 10 of FIG. 10C, forexample, a portion of the conductive layer 110 in each stackingstructure 112 and closest portions of the dielectric layer 114, thesemiconductor layer 116 and the conductive pillars 118 in a cell regionCR laterally adjacent to this portion of the conductive layer 110constitute the transistor, e.g. a field effect transistor (FET), whichis functioned as a memory cell MC included in the three-dimensionalmemory device 10. In those embodiments where the dielectric layers 114are formed of a ferroelectric material, dipole moments in oppositedirections can be stored in the dielectric layer 114. Accordingly, theFET has different threshold voltages in corresponding to the dipolemoments, thus the FET can be identified as having different logicstates. In these embodiments, the memory cell MC is a ferroelectric FET.On the other hand, in those embodiments where the dielectric layer 114is a charge trap layer, charges may be stored in the dielectric layer114, thus the FET may have different threshold voltages depending on theamount of charge stored in the dielectric layer 114. Accordingly, theFET can be identified as having different logic states as well. In theseembodiments, the memory cell MC may be referred as a charge trap flash(CTF) transistor.

The three-dimensional memory device 10 may include multiple memory cellsMC arranged in a form of array laterally and vertically. For example,the conductive layers 110 stacked along a vertical direction (e.g., thedirection Z) in each stacking structure 112 as well as portions of thedielectric layer 114, the semiconductor layer 116 and the pair ofconductive pillars 118 in a cell region CR aside these conductive layers110 form a stack of memory cells MC. In addition, multiple stacks of thememory cells MC may be arranged along an extending direction (e.g., thedirection Y, may be referred to as a trench direction) of the trenches106, where the trenches 106 are arranged side-by-side (e.g., inparallel) along a lateral direction (e.g., the direction X). The lateraldirection (e.g., X), the trench direction (e.g., Y) and the verticaldirection (e.g., Z) may be different from one another. For example, thedirection X and the direction Y are substantially perpendicular to thedirection Z, and the direction X is substantially perpendicular to thedirection Y. In some embodiments, the dielectric layer 114, thesemiconductor layer 116 and a pair of conductive pillars 118 in the samecell region CR are shared by adjacent stacks of memory cells MCincluding the conductive layers 110 at opposite sides of this cellregion CR, and conductive channels of these memory cells MC are formedin different sections of the semiconductor layer 116. In the embodimentsof which the three-dimensional memory device 10 manufactured by themethod of FIG. 2A and FIG. 2B, at least three sides of each of theconductive pillars 118 are covered by a respective one of thesemiconductor layers 116 and a respective one of the dielectric layers114, and at least three sides of each of the semiconductor layers 116are covered by a respective one of the dielectric layers 114.

FIG. 12 is an equivalent circuit diagram of a portion of athree-dimensional memory device 10 shown in FIG. 10A.

Referring to FIG. 10A and FIG. 12 , the conductive layers 110 in eachstacking structure 112 shown in FIG. 10A may be functioned as word linesWL as shown in FIG. 12 . The word lines WL are arranged along thevertical direction (e.g., the direction Z). Each word line WL connectsgate terminals G of two laterally adjacent columns of the memory cellsMC (e.g., on the X-Y plane). In addition, each pair of conductivepillars 118 in one of the cell regions CR shown in FIG. 10A separatelyconnect to source and drain terminals S, D of the memory cells MCstacked along the vertical direction (e.g., the direction Z) as shown inFIG. 12 . As shown in FIG. 12 , the gate terminals G of each stack ofthe memory cells MC are respectively connected to one of the word linesWL. In addition, the source terminals S of each stack of the memorycells MC are connected together by one of the conductive pillars 118,and the drain terminals D of each stack of the memory cells MC areconnected together by another one of the conductive pillars 118. Inother words, channels CH between the source and drain terminals S, D ofeach stack of the memory cells MC are connected in parallel.Accordingly, each stack of the memory cells MC may be regarded as beingconnected by a NOR-flash configuration, and the three-dimensional memorydevice 10 may be referred as a three-dimensional NOR memory device.

FIG. 13 is a schematic cross-sectional view illustrating a semiconductorstructure 20 in accordance with some embodiments of the disclosure.

Referring to FIGS. 10A-10C and FIG. 13 , the semiconductor structure 20shown in FIG. 13 includes the three-dimensional memory device 10 asdescribed with reference to FIGS. 10A-10C. In those embodiments wherethe underlying structure 102 of the three-dimensional memory device 10is an etching stop layer, a CMOS integrated circuit LC may lie under theunderlying structure 102, and the CMOS integrated circuit LC may also bereferred as a CMOS-under-array (CUA). Although not shown, the conductivelayers 110 and the conductive pillars 118 may be routed to the CMOSintegrated circuit LC, and the three-dimensional memory device 10 may becontrolled by the CMOS integrated circuit LC. The details of electricalconnections between the CMOS integrated circuit LC and the conductivelayers 110 and between the CMOS integrated circuit LC and the conductivepillars 118 will be discussed later in greater detail in conjunctionwith FIG. 14A through FIG. 14B and FIG. 15A through FIG. 15B. In someembodiments, the three-dimensional memory device 10 as described withreference to FIGS. 10A-10C is embedded in a BEOL structure of thesemiconductor structure 20 shown in FIG. 13 , and the CMOS integratedcircuit LC is formed on a front-end-of-line (FEOL) structure of thesemiconductor structure 20 shown in FIG. 13 .

In some embodiments, the CMOS integrated circuit LC is built on asemiconductor substrate 200. The semiconductor substrate 200 may be asemiconductor wafer or a semiconductor-on-insulator (SOI) wafer. TheCMOS integrated circuit LC may include active devices formed on asurface region of the semiconductor substrate 200. In some embodiments,the active devices include metal-oxide-semiconductor (MOS) transistors202. The MOS transistors 202 may respectively include a gate structure204 formed over the semiconductor substrate 200. In some embodiments,the gate structure 204 includes a gate electrode 206, a gate dielectriclayer 208 and a gate spacer 210. The gate dielectric layer 208 mayspread between the gate electrode 206 and the semiconductor substrate200, and may or may not further cover a sidewall of the gate electrode206. The gate spacer 210 may laterally surround the gate electrode 206and the gate dielectric layer 208. Further, the MOS transistor 202 mayfurther include source/drain regions 212. The source/drain regions 212may be formed in the semiconductor substrate 200, and are located atopposite sides of the gate structure 204. In some embodiments, thesource/drain regions 212 may be epitaxial structures, and may protrudefrom a surface of the semiconductor substrate 200. It should be notedthat, although the MOS transistors 202 are depicted as planar-type MOStransistors that forms conductive channels (not shown) along the surfaceof the semiconductor substrate 200, the MOS transistors 202 mayalternatively be fin-type MOS transistors (or referred as finFET),gate-all-around (GAA) FETs or the like.

In some embodiments, the CMOS integrated circuit LC further includesdielectric layers 214 stacked on the semiconductor substrate 200, andincludes contact plugs 216 and interconnections 218 formed in the stackof dielectric layers 214. A bottommost dielectric layer 214 maylaterally surround the gate structures 204, and cover the source/drainregions 212. Some of the contact plugs 216 may penetrate throughbottommost ones of the dielectric layers 214, in order to establishelectrical connection with the source/drain regions 212, while others ofthe contact plugs 216 may stand on the gate structures 204 andelectrically connect to the gate electrodes 206 of the gate structures204. The interconnections 218 may spread on the contact plugs 216, andare electrically connected to the contact plugs 216. Theinterconnections 218 may include conductive traces and conductive vias.The conductive traces respectively lie on one of the dielectric layers214, whereas the conductive vias respectively penetrate through one ormore of the dielectric layers 214 and electrically connect to one ormore of the conductive traces.

In some embodiments, the three-dimensional memory device 10 is disposedon the stack of dielectric layers 214. In these embodiments, theconductive layers 110 and the conductive pillars 118 of thethree-dimensional memory device 10 may be routed to the interconnections218 in the stack of dielectric layers 214 by conductive paths (notshown) extending through the underlying structure 102 and topmost onesof the dielectric layers 214. For example, the conductive layers 110(e.g., word lines having end portions with a staircase configurationbeing exposed from the stacking structures 112) may be routed to wordline drivers formed by some of the active devices interconnected by aportion of the interconnections 218, and the conductive pillars 118(e.g., bit line and/or source line) may be routed to sense amplifiersformed by others of the active devices interconnected by another portionof the interconnections 218.

FIG. 14A is a schematic three-dimensional view illustrating athree-dimensional memory device 10 a in accordance with some embodimentsof the disclosure. FIG. 14B is a schematic cross-sectional view of aportion of the three-dimensional memory device 10 a along an extendingdirection of the source line SL2 shown in FIG. 14A. Thethree-dimensional memory device 10 a shown in FIG. 14A and FIG. 14B issimilar to the three-dimensional memory device 10 as described withreference to FIGS. 10A-10C. Only differences therebetween will bedescribed, the same or the like part would not be repeated again. Inaddition, a dielectric layer 302 to be described with reference to FIG.14B are omitted in FIG. 14A.

Referring to FIG. 14A, in some embodiments, the three-dimensional memorydevice 10 a further includes bit lines BL and source lines SL. The bitlines BL and the source lines SL are electrically connected to theconductive pillars 118 through, for example, conductive vias CV. Theconductive pillars 118 in each one of the cell regions CR are connectedto one of the bit lines BL and one of the source lines SL, respectively.In some embodiments, the bit lines BL and the source lines SL extendalong a row direction (e.g., the direction X) intersected with thecolumn direction (e.g., the direction Y) along which the cell regions CRbetween adjacent stacking structures 112 are arranged. In thoseembodiments where columns of the cell regions CR are alternately offsetfrom others, the conductive pillars 118 in adjacent columns of the cellregions CR may be connected to different bit lines BL and differentsource lines SL. For example, the conductive pillars 118 in odd columnsof the cell regions CR may be connected to bit lines BL1 and sourcelines SL1, whereas the conductive pillars 118 in even column of the cellregions CR may be connected to bit lines BL2 and source lines SL2.Consequently, the memory cells MC in adjacent columns of the cellregions CR can be controlled by different bit lines BL (e.g., the bitlines BL1 and the bit lines BL2) and different source lines SL (e.g.,the source lines SL1 and the source lines SL2), thus interferencebetween the memory cells MC in adjacent columns of the cell regions CRcan be reduced.

Referring to FIG. 14A and FIG. 14B, in some embodiments, the bit linesBL and the source lines SL extend above the stacking structures 112. Thebit lines BL, the source lines SL and the conductive vias CV may beformed in a stack of dielectric layers 302 formed on the stackingstructures 112. The conductive vias CV may penetrate through bottommostone(s) of the dielectric layers 302, to establish electrical connectionfrom the conductive pillars 118 to the bit lines BL and the source linesSL lying above the conductive vias CV. In those embodiments where theunderlying structure 102 is an etching stop layer formed over a CMOSintegrated circuit (e.g., the CMOS integrated circuit LC as describedwith reference to FIG. 13 ), the bit lines BL and the source lines SLmay be further routed to the underlying CMOS integrated circuit througha conductive path (not shown) formed aside the stacking structures 112and penetrating through the underlying structure 102.

FIG. 15A is a schematic three-dimensional view illustrating athree-dimensional memory device 10 b in accordance with some embodimentsof the disclosure. FIG. 15B is a schematic cross-sectional view of aportion of the three-dimensional memory device 10 b along an extendingdirection of one (e.g., SL1) of the source lines SL shown in FIG. 15A.The three-dimensional memory device 10 b shown in FIG. 15A and FIG. 15Bis similar to the three-dimensional memory device 10 a as described withreference to FIG. 14A and FIG. 14B. Only differences therebetween willbe described, the same or the like part would not be repeated again.

Referring to FIG. 15A and FIG. 15B, in some embodiments, the sourcelines SL extend below the underlying structure 102, while the bit linesBL extend above the stacking structures 112. In these embodiments, asshown in FIG. 15B, the source lines SL may be formed in the stack ofdielectric layers 214 (as described with reference to FIG. 11 ) belowthe underlying structure 102. The source lines SL may lie on one of thedielectric layers 214. In addition, conductive vias CV′ may be furtherformed to electrically connect some of the conductive pillars 118 to theunderlying source lines SL. The conductive vias CV′ may extend frombottom surfaces of some of the conductive pillars 118, and penetratethrough the underlying dielectric layers 114, the underlying structure102 and topmost one(s) of the dielectric layers 214, to reach the sourcelines SL.

In alternative embodiments, locations of the source lines SL and the bitlines BL are switched. In other words, the source lines SL may extendabove the stacking structures 112, and may be electrically connected tosome of the conductive pillars 118 as described with reference to FIG.14A and FIG. 14B. On the other hand, the bit lines BL may extend in thedielectric layers 214 below the stacking structures 112, and may beelectrically connected to others of the conductive pillars 118 throughthe conductive vias CV′.

In the disclosure, the three-dimensional memory device 10, 10 a and 10 bdepicted in FIG. 10A, FIG. 14A and FIG. 15A are formed with theconductive pillars 118 arranged in a staggered layout in adjacenttrenches 106, for example. For example, the conductive pillars 118formed in the odd trenches 106 extending along the direction Y aresubstantially aligned with each other in the direction X, while theconductive pillars 118 formed in the even trenches 106 extending alongthe direction Y are substantially aligned with each other in thedirection X. In other words, the conductive pillars 118 formed in theodd trenches 106 are offset from (not aligned with) the conductivepillars 118 formed in the even trenches 106 in the direction X.

However, the disclosure is not limited thereto; alternatively, theconductive pillars 118 of a three-dimensional memory device (e.g., 30depicted in FIG. 16A and FIG. 16B) may be arranged in aligned layout(e.g., in a periodic fashion).

FIG. 16A is a schematic three-dimensional view illustrating athree-dimensional memory device 30 in accordance with some embodimentsof the disclosure, and FIG. 16B is a schematic cross-sectional view ofthe three-dimensional memory device 30 along a line A-A′ shown in FIG.16A. The three-dimensional memory device 30 shown in FIG. 16A and FIG.16B is similar to the three-dimensional memory device 10 as describedwith reference to FIGS. 10A-10C. Only differences therebetween will bedescribed, the same or the like part would not be repeated again. Forexample, as shown in FIG. 16A and FIG. 16B, the conductive pillars 118formed in the odd trenches 106 extending along the direction Y and theconductive pillars 118 formed in the even trenches 106 extending alongthe direction Y are all substantially aligned with one another in thedirection X. In other words, the conductive pillars 118 formed in theodd trenches 106 are lined up with the conductive pillars 118 formed inthe even trenches 106 in the direction X, respectively.

FIG. 17 , FIG. 18 and FIG. 19 each are a schematic enlarged plan viewsillustrating a portion of a three-dimensional memory device (e.g. 40, 50and 60) in accordance with some embodiments of the disclosure,respectively. These three-dimensional memory devices 40, 50 and 60 aresimilar to the three-dimensional memory device 10 as described withreference to FIG. 10A-10C. Only differences therebetween will bedescribed, the same or the like parts would not be repeated again forsimplicity.

For example, the three-dimensional memory devices 10, 10 a, 10 b and 30depicted in FIG. 10A, FIG. 14A, FIG. 15A and FIG. 16A are formed withthe cell regions CR and the conductive pillars 118 each formed in asubstantially rectangular top view shape. However, the disclosure is notlimited thereto; alternatively, the cell regions CR and the conductivepillars 118 each may be formed in a substantially circular top viewshape as shown in the three-dimensional memory device 40 depicted inFIG. 17 . Alternatively, the conductive pillars 118 depicted in FIG. 17may be formed in a substantially elliptical or oval top view shape. Inother embodiments, the conductive pillars 118 each may be formed in asubstantially elliptical top view shape while the cell regions CR eachare formed in a substantially rectangular top view shape, as shown inthe three-dimensional memory device 50 depicted in FIG. 18 .Alternatively, the conductive pillars 118 depicted in FIG. 18 may beformed in a substantially circular or oval top view shape. In furtherembodiments, the conductive pillars 118 each may be formed in asubstantially truncated-elliptical top view shape while the cell regionsCR each are formed in a substantially rectangular top view shape, asshown in the three-dimensional memory device 50 depicted in FIG. 19 .Alternatively, the conductive pillars 118 depicted in FIG. 19 may beformed in a substantially truncated-oval or truncated-circular top viewshape.

In the three-dimensional memory devices 40, 50 and 60, the first liners122 each are conformally cover a respective one of the first main layers120 to form the first isolation structures 128, and the second liners126 each are conformally cover a respective one of the second mainlayers 124 to form the second isolation structures 130. In thedisclosure, the first and second liners 120, 122 of the first and secondisolation structures 128, 130 act as the shielding layers for preventingmetal filling leakage paths formation inside a single one cell region CRor among neighboring cell regions CR between the conductors (e.g. theadjacent conductive pillars 118 within one cell region CR and theconductive layers 110 located in the adjacent stacking structures 112)to improve the device performance of the three-dimensional memorydevices 40, 50 and 60.

As shown in the plan views of FIG. 17 through FIG. 19 (e.g., the X-Yplane), for example, a distance between the paired conductive pillars118 in one cell region CR is increased from a center of a trench 106 toan edge of the trench 106 along a direction perpendicular to anextending direction of the trench 106. With such configuration, thechannel length of the FET in one cell region CR and the area of the cellregion CR maintain the same while the overall area of the conductivepillars 118 is increased, thereby reducing the contact resistance in theconductive pillars 118 (e.g. source/drain regions) while the memorydensity will maintain the same. On the other hands, in the embodimentsshown in FIG. 18 and FIG. 19 , the dielectric layers 114′ is formed inthe cell regions CR to cover the sidewalls SW112 of the correspondingstacking structures 112 without extending over the sidewalls of theimmediately adjacent second isolation structures 130; thereby not onlyincreasing the overall area of the conductive pillars 118 but alsoreducing the impedance of the memory cells MC. Alternatively, as shownin FIG. 19 , the semiconductor layers 116′ may also be formed in thecell regions CR to cover the dielectric layers 114′ located on thesidewalls SW112 of the corresponding stacking structures 112 and notextend over the sidewalls of the immediately adjacent second isolationstructures 130 to further increases the overall area of the conductivepillars 118 and reduce the impedance of the memory cells MC. A materialof the dielectric layers 114′ may be the same as or the similar to thematerial of the dielectric layers 114 as described in FIG. 8A throughFIG. 8C, a material of the semiconductor layers 116′ may be the same asor the similar to the material of the semiconductor layers 116 asdescribed in FIG. 8A through FIG. 8C, and thus are omitted for brevity.

A method for forming the dielectric layers 114′ may include, but notlimited to, selectively depositing a dielectric material only on thesidewalls SW112 of the corresponding stacking structures 112 and the topsurface of the underlying structure 102 exposed by the cell regions CRto form the dielectric layers 114′. Alternatively, a dielectric materialmay be globally formed on sidewalls and bottom surfaces of the cellregions CR and removing the dielectric material from the sidewalls ofthe immediately adjacent second isolation structures 130 to form thedielectric layers 114′ by patterning. A method for forming thesemiconductor layers 116′ may include, but not limited to, selectivelydepositing a semiconductor material only on the sidewalls of thecorresponding dielectric layers 114′ to form the semiconductor layers116′. Alternatively, a semiconductor material may be globally formedover the cell regions CR disposed with the dielectric layer 114′ andremoving the semiconductor material from the sidewalls of theimmediately adjacent second isolation structures 130 to form thesemiconductor layers 116′ by patterning. The patterning may includephotolithography and etching processes.

In addition, the three-dimensional memory device 30 may also adopt thetop view layouts of the cell regions CR in the three-dimensional memorydevices 40-60. The disclosure is not limited thereto.

In some embodiments, the three-dimensional memory devices 10 through 60respectively depicted in FIGS. 10A, 14A, 15A, 16A and 17-19 are formedwith the stacking structures 112 each having continuously (e.g., evenly)vertical sidewalls SW112 (as described with reference to FIG. 6A throughFIG. 6C). However, the disclosure is not limited thereto; alternatively,a three-dimensional memory device (e.g., 70 depicted in FIG. 20A andFIG. 20B) may include a plurality of the stacking structures 112′ eachhaving sidewalls SW112′ being discontinuously (e.g., unevenly) vertical.

FIG. 20A and FIG. 20B are schematic various views of a three-dimensionalmemory device 70 in accordance with some embodiments of the disclosure,where FIG. 20A is a schematic three-dimensional view illustrating thethree-dimensional memory device 70, and FIG. 16B is a schematiccross-sectional view along a line A-A′ shown in FIG. 20A. Thethree-dimensional memory device 70 shown in FIG. 20A and FIG. 20B issimilar to the three-dimensional memory device 10 as described withreference to FIGS. 10A-10C; the difference is that, for thethree-dimensional memory device 70 depicted in FIG. 20A and FIG. 20B,stacking structures 112′ are adopted, instead the stacking structures112. Only differences therebetween will be described, the same or thelike part would not be repeated for simplicity.

Referring to FIG. 20A and FIG. 20B, in some embodiments, the stackingstructures 112′ each include a plurality of first dielectric layers 104Aand a plurality of conductive layers 110 a. The first dielectric layers104A and the conductive layers 110 a are stacked on the underlyingstructure 102 in alternation. Sidewalls SW110 a of the conductive layers110 a and sidewalls SW104A of the first dielectric layers 104A maytogether referred to as the sidewalls SW112′ of the stacking structures112′. In some embodiments, the sidewalls SW110 a of the conductivelayers 110 a are offset from the sidewalls SW104A of the firstdielectric layers 104A at outermost sides (e.g., the sidewalls SW112′)of each stacking structures 112′ exposed by the trenches 106 in astacking direction (e.g., the direction Z) of the first dielectriclayers 104A and the conductive layers 110 a, as shown in FIG. 20B. Inother words, the sidewalls SW110 a of the conductive layers 110 a arenot coplanar to and levelled with the sidewalls SW104A of the firstdielectric layers 104A, but are laterally recessed from the sidewallsSW104A of the first dielectric layers 104A. That is, the sidewallsSW112′ of the stacking structures 112′ each have a concave-convexsurface. For example, in a cross-section of FIG. 20B, the sidewallsSW112′ each include a substantially non-straight line. The sidewallsSW110 a of the conductive layers 110 a may be spaced apart from thesidewalls SW104A of the first dielectric layers 104A by recesses R3,respectively. In some embodiments, the width W of the recesses R3 isapproximately ranging from 80 nm to 150 nm.

For example, as shown in FIG. 20A and FIG. 20B, the stacking structures112′ are laterally spaced apart from one another by the trenches 106,and directly stand on the underlying structure 102. The dielectriclayers 114, the semiconductor layers 116 and the conductive pillars 118are located in the cell regions CR within the trenches 106, where aportion of the conductive layer 110 a in each stacking structure 112′and closest portions of the dielectric layer 114, the semiconductorlayer 116 and the conductive pillars 118 in a cell region CR laterallyadjacent to this portion of the conductive layer 110 a constitute thetransistor, e.g. a FET, which is functioned as a memory cell MC includedin the three-dimensional memory device 70. In some embodiments, thefirst isolation structures 128 are located within the cell regions CR toseparate apart and physically isolate the conductive pillars 118 in eachcell region CR, while the second isolation structures 130 are locatedoutside the cell regions CR to separate apart and physically isolate thecell regions CR in each trench 106. In the disclosure, the first andsecond liners 120, 122 of the first and second isolation structures 128,130 act as the shielding layers for preventing metal filling leakagepaths formation inside a single one cell region CR or among neighboringcell regions CR between the conductors (e.g. the adjacent conductivepillars 118 within one cell region CR and the conductive layers 110 alocated in the adjacent stacking structures 112′) to improve the deviceperformance of the three-dimensional memory device 70.

A method for forming the three-dimensional memory device 70 includingthe stacking structures 112′ may include, but not limited to, afterperforming the process as described in FIG. 6A through FIG. 6C (e.g.,step S106 of FIG. 2A) and prior to the process as described in FIG. 7Athrough FIG. 7C (e.g., step S108 of FIG. 2A), laterally recessing theconductive layers 110 with respect to the first dielectric layer 104A toform the recesses R3 in accordance with step S107 of FIG. 2A for formingthe conductive layers 110 a, such that the stacking structures 112′ aremanufactured. For example, a method for laterally recessing theconductive layers 110 includes an etching process, such as an isotropicetching process. In some embodiments, during the formation of theconductive layers 110 a, the first dielectric layers 104A and theunderlying structure 102 may be barely etched (e.g., substantiallyintact) during the etching process as having sufficient etchingselectivity with respect to the conductive layers 110. After theformation of the recesses R3, the recesses R3 may be spatiallycommunicated with the trenches 106 to expose portions of the mainsurfaces of the first dielectric layers 104 being in contact with theconductive layers 110.

After the formation of the stacking structures 112′, the processes ofthe steps S108-S122 of FIG. 2A and the steps S122 a-S122 d of FIG. 2Bare performed on the stacking structures 112′ so as to manufacture thethree-dimensional memory device 70. The formation and material of eachof the underlying structure 102, the first dielectric layer 104A, theconductive layers 110, the dielectric layer 114, the semiconductorlayers 116, the conductive pillars 118, the first isolation structures128 (including the first liners 120 and the first main layers 124) andthe second isolation structures 130 (including the second liners 122 andthe second main layers 126) have been previously described in FIG. lAthrough FIG. 10C in conjunction with FIG. 2A and FIG. 2B, and thus arenot repeated herein for simplicity.

In addition, the three-dimensional memory device 70 may also adopt thearrangement of the cell regions CR in the three-dimensional memorydevice 30 and/or the top view layouts of the cell regions CR in thethree-dimensional memory devices 40-60. The disclosure is not limitedthereto.

In accordance with some embodiments, a memory device includes a firststacking structure, a second stacking structure, a plurality of firstisolation structures, gate dielectric layers, channel layers and channellayers. The first stacking structure includes a plurality of first gatelayers, and a second stacking structure includes a plurality of secondgate layers, where the first stacking structure and the second stackingstructure are located on a substrate and separated from each otherthrough a trench. The first isolation structures are located in thetrench, where a plurality of cell regions are respectively confinedbetween two adjacent first isolation structures of the first isolationstructures in the trench, where the first isolation structures eachincludes a first main layer and a first liner surrounding the first mainlayer, where the first liner separates the first main layer from thefirst stacking structure and the second stacking structure. The gatedielectric layers are respectively located in one of the cell regions,and cover opposing sidewalls of the first stacking structure and thesecond stacking structure as well as opposing sidewalls of the firstisolation structures. The channel layers respectively cover an innersurface of one of the gate dielectric layers. The conductive pillarsstand on the substrate within the cell regions, and are laterallysurrounded by the channel layers, where at least two of the conductivepillars are located in each of the cell regions, and the at least twoconductive pillars in each of the cell regions are laterally separatedfrom one another.

In accordance with some embodiments, a memory device includes a firststacking structure, a second stacking structure, a plurality of firstisolation structures, gate dielectric layers, channel layers, conductivepillars, and a plurality of second isolation structures. The firststacking structure and the second stacking structure are formed on asubstrate and laterally spaced apart from each other through a trench,where the first stacking structure includes first insulating layers andfirst gate layers alternately stacked on the substrate, the secondstacking structure includes second insulating layers and second gatelayers alternately stacked on the substrate, and the first stackingstructure and the second stacking structure are separated from eachother. The first isolation structures are located in the trench, where aplurality of cell regions are respectively confined between two adjacentfirst isolation structures of the first isolation structures in thetrench. The gate dielectric layers are respectively located in one ofthe cell regions, and cover opposing sidewalls of the first stackingstructure and the second stacking structure. The channel layersrespectively cover an inner surface of one of the gate dielectriclayers. The conductive pillars stand on the substrate within the cellregions, and are laterally surrounded by the channel layers, where atleast two of the conductive pillars are located in each of the cellregions. The second isolation structures are respectively located in oneof the cell regions and separate the at least two of the conductivepillars in each of the cell regions, where at least one of the firstisolation structures and the second isolation structures each includes amain layer and a liner surrounding and in contact with the main layer.

In accordance with some embodiments, a method of manufacturing a memorydevice includes the following steps: forming a multilayer stackcomprising insulating layers and sacrificial layers arranged inalternation; forming trenches in the multilayer stack; replacing thesacrificial layers with gate layers; forming dummy dielectric structuresin the trenches to form cell regions separated from one another; formingmemory films on sidewalls of the cell regions; forming channel layers onthe memory films; forming conductive structures to fill up the cellregions; patterning the conductive structures to form at least twoconductive pillars in each of the cell regions; removing the dummydielectric structures; and forming first isolation structures betweenthe at least two conductive pillars in each of the cell regions andforming second isolation structures between the cell regions, whereinforming the first isolation structures includes forming first liners onopposite sidewalls of the at least two of the conductive pillars andopposite sidewalls of a respective one of the channel layers exposed bythe at least two of the conductive pillars in each of the cell regionsby ALD and filling up the cell regions with a first dielectric materialto form the first isolation structures respectively surrounded by thefirst liners.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the disclosure.Those skilled in the art should appreciate that they may readily use thedisclosure as a basis for designing or modifying other processes andstructures for carrying out the same purposes and/or achieving the sameadvantages of the embodiments introduced herein. Those skilled in theart should also realize that such equivalent constructions do not departfrom the spirit and scope of the disclosure, and that they may makevarious changes, substitutions, and alterations herein without departingfrom the spirit and scope of the disclosure.

What is claimed is:
 1. A method of manufacturing a memory device,comprising: forming a multilayer stack comprising insulating layers andsacrificial layers arranged in alternation; forming trenches in themultilayer stack; replacing the sacrificial layers with gate layers;forming dummy dielectric structures in the trenches to form cell regionsseparated from one another; forming memory films on sidewalls of thecell regions; forming channel layers on the memory films; formingconductive structures to fill up the cell regions; patterning theconductive structures to form at least two conductive pillars in each ofthe cell regions; removing the dummy dielectric structures; and formingfirst isolation structures between the at least two conductive pillarsin each of the cell regions and forming second isolation structuresbetween the cell regions, wherein forming the first isolation structurescomprises: forming first liners on opposite sidewalls of the at leasttwo of the conductive pillars and opposite sidewalls of a respective oneof the channel layers exposed by the at least two of the conductivepillars in each of the cell regions by ALD; and filling up the cellregions with a first dielectric material to form the first isolationstructures respectively surrounded by the first liners.
 2. The method ofclaim 1, wherein forming the second isolation structures comprises:forming, on opposite sidewalls of two adjacent cell regions in each ofthe trenches and the opposite sidewalls of each of the trenches exposedby the two adjacent cell regions, second liners by ALD; and filling upgaps respectively sandwiched between the two adjacent cell regions ineach of the trenches with a second dielectric material to form thesecond isolation structures surrounded by the second liners.
 3. Themethod of claim 1, prior to forming the dummy dielectric structures inthe trenches and after replacing the sacrificial layers with the gatelayers, further comprising: laterally recessing the gate layers inrespect to the insulating layers.
 4. The method of claim 1, whereinforming the dummy dielectric structures in the trenches to form the cellregions separated from one another comprises: forming a dummy dielectricmaterial in the trenches; and removing portions of the dummy dielectricmaterial to form the dummy dielectric structures separating the cellregions separated from one another.
 5. The method of claim 1, whereinforming the memory films on sidewalls of the cell regions comprises:conformally forming the memory films on the cell regions to respectivelycover all sidewalls and bottom surface of each of the cell regions. 6.The method of claim 1, wherein forming the memory films on sidewalls ofthe cell regions comprises: selectively forming the memory films on thecell regions to respectively cover sidewalls of each of the cell regionslocated at the multilayer stack.
 7. A method of manufacturing a memorydevice, comprising: forming a multilayer stack comprising insulatinglayers and sacrificial layers arranged in alternation along a verticaldirection over a substrate; patterning the multilayer stack into aplurality of stacking structures being separated from each other andstanding over the substrate; replacing, in the plurality of stackingstructures, the sacrificial layers with gate layers; disposing dummydielectric structures next to the plurality of stacking structures overthe substrate, the dummy dielectric structures propping again sidewallsof the plurality of stacking structures, the plurality of stackingstructures being arranged along a first horizontal direction, the dummydielectric structure arranged along a second horizontal direction,wherein a cell regions is confined by two adjacent of the plurality ofstacking structures and two adjacent of the dummy dielectric structures;sequentially forming memory films, channel layers and conductivestructures in the cell regions to fill the cell regions; patterning theconductive structures to form at least two conductive pillars in each ofthe cell regions separating from each other by a first recess; removingthe dummy dielectric structures to form second recesses; forming firstisolation structures in the first recesses included in the cell regions,comprising: forming first liners to line sidewalls of the first recessesby ALD; and filling the first recesses with a first dielectric materialto form the first isolation structures respectively surrounded by thefirst liners; and forming second isolation structures in the secondrecesses, comprising: forming second liners to line sidewalls of thesecond recesses by ALD; and filling the second recesses with a seconddielectric material to form the second isolation structures respectivelysurrounded by the second liners.
 8. The method of claim 7, wherein in ahorizontal cross-section of the memory device, shapes of the cellregions is formed to be circular, oval or elliptical, wherein for eachof the cell regions: a shape of the memory film is formed to include acircular annulus frame, an oval annulus frame, or an elliptical annulusframe; a shape of the channel layer is formed to include a circularannulus frame, an oval annulus frame, or an elliptical annulus frame;and shapes of the at least two conductive pillars are formed to includecircular shapes, oval shapes or elliptical shapes.
 9. The method ofclaim 7, wherein in a horizontal cross-section of the memory device,shapes of the cell regions is formed to be quadrilateral, wherein foreach of the cell regions: a shape of the memory film is formed toinclude a strip shape; a shape of the channel layer is formed to includean annulus frame having an outer sidewall of a quadrilateral shape andan inner sidewall of a circular, oval or elliptical shape; and shapes ofthe at least two conductive pillars are formed to include circularshapes, oval shapes or elliptical shapes.
 10. The method of claim 7,wherein in a horizontal cross-section of the memory device, shapes ofthe cell regions is formed to be quadrilateral, wherein for each of thecell regions: a shape of the memory film is formed to include a stripshape; a shape of the channel layer is formed to include a strip shape;and shapes of the at least two conductive pillars are formed to includetruncated-circular shapes, truncate-oval shapes or truncated-ellipticalshapes.
 11. The method of claim 7, wherein in a horizontal cross-sectionof the memory device, for each of the cell regions: a first width of thefirst isolation structure at a center of a respective cell region isless than a second width of the first isolation structure at edges ofthe respective cell region, where the first width and the second widthare measured along the second horizontal direction.
 12. The method ofclaim 7, wherein in a horizontal cross-section of the memory device, foreach of the second recesses: a third width of the second isolationstructure at a center of a respective second recess is less than afourth width of the first isolation structure at edges of the secondrecess, where the third width and the fourth width are measured alongthe second horizontal direction.
 13. The method of claim 7, whereindisposing the dummy dielectric structures next to the plurality ofstacking structures over the substrate comprises: forming a dummydielectric material between every two adjacent of the plurality ofstacking structure over the substrate; and removing portions of thedummy dielectric material to form the dummy dielectric structures beingdisposed next to the plurality of stacking structures over thesubstrate.
 14. A method of manufacturing a memory device, comprising:forming a plurality of stacking structures being separated from eachother and standing over a substrate, the plurality of stackingstructures each comprising dielectric layers and gate layers arranged inalternation; laterally recessing portions of the gate layers in respectto the dielectric layers to form a plurality of lateral recesses;disposing dummy dielectric structures next to the plurality of stackingstructures over the substrate to form cell regions each being confinedby two adjacent of the plurality of stacking structures and two adjacentof the dummy dielectric structures; sequentially forming memory films,channel layers and conductive structures in the cell regions and a partof the lateral recess; patterning the conductive structures to form atleast two conductive pillars in each of the cell regions separating fromeach other by a first recess; and forming first isolation structures inthe first recesses included in the cell regions and the lateral recess,comprising: forming first liners to line sidewalls of the first recessesand the lateral recesses by ALD; and filling the first recesses with afirst dielectric material to form the first isolation structuresrespectively surrounded by the first liners.
 15. The method of claim 14,further comprising: removing the dummy dielectric structures to formsecond recesses prior to forming the first isolation structures; andforming second isolation structures in the second recesses and thelateral recess, comprising: forming second liners to line sidewalls ofthe second recesses and the lateral recesses by ALD; and filling thesecond recesses with a second dielectric material to form the secondisolation structures respectively surrounded by the second liners. 16.The method of claim 15, wherein forming the first isolation structuresand the forming the second isolation structure are simultaneouslyperformed in a same step.
 17. The method of claim 14, wherein in ahorizontal cross-section of the memory device, shapes of the cellregions is formed to be circular, oval or elliptical, wherein for eachof the cell regions: a shape of the memory film is formed to include acircular annulus frame, an oval annulus frame, or an elliptical annulusframe; a shape of the channel layer is formed to include a circularannulus frame, an oval annulus frame, or an elliptical annulus frame;and shapes of the at least two conductive pillars are formed to includecircular shapes, oval shapes or elliptical shapes.
 18. The method ofclaim 14, wherein in a horizontal cross-section of the memory device,shapes of the cell regions is formed to be quadrilateral, wherein foreach of the cell regions: a shape of the memory film is formed toinclude a strip shape; a shape of the channel layer is formed to includean annulus frame having an outer sidewall of a quadrilateral shape andan inner sidewall of a circular, oval or elliptical shape; and shapes ofthe at least two conductive pillars are formed to include circularshapes, oval shapes or elliptical shapes.
 19. The method of claim 14,wherein in a horizontal cross-section of the memory device, shapes ofthe cell regions is formed to be quadrilateral, wherein for each of thecell regions: a shape of the memory film is formed to include a stripshape; a shape of the channel layer is formed to include a strip shape;and shapes of the at least two conductive pillars are formed to includetruncated-circular shapes, truncate-oval shapes or truncated-ellipticalshapes.
 20. The method of claim 14, wherein disposing dummy dielectricstructures next to the plurality of stacking structures over thesubstrate comprises: forming a dummy dielectric material between everytwo adjacent of the plurality of stacking structure over the substrate;and removing portions of the dummy dielectric material to form the dummydielectric structures being disposed next to the plurality of stackingstructures over the substrate.